Norm Nadel wrote:
>
> How difficult is it to calibrate the OM-2n ?
It's easy -- after the first 100-200 or so! ;^)
Actually, to do the job properly requires some test equipment -- a
shutter speed tester, a calibrated light source, and an exposure
tester. You'll need to remove the top cover, the cover below the
mirror, and replace the bottom cover with one that's been cut off at the
MD opening just to hold the batteries in place.
First, assuming all the mechanical functions are OK, you've got to set
the curtains so they travel across the focal aperture at the correct
speed. If they don't move at the proper speed, none of the other
adjustments are going to do any good. And if one curtain is faster than
the other, one side of the photo will get more light than the other --
not a good thing!
Once that's done, you'll need to adjust the high speeds by changing the
position of the trigger switch -- that's what tells the camera's timing
circuit that the shutter has begun to open. There's an eccentric for
that, but hardly anybody uses it -- we just make minute bends to the
contacts or the frame that holds them.
Occasionally you run into difficulties with what Olympus calls the "Auto
Limiter" -- a mechanical device that limits the highest speed the camera
will deliver. If it's off, that can make the high speeds very difficult
to adjust.
Then adjust the lower speeds, primarily checking 1/8th second. There's
a VR on the main circuit for that. Then you'll want to re-check the
high speeds again, of course.
Once the manual speeds are in tolerance, you can check the actual
exposure at the film plane. This requires a special sensor that has the
same reflectance as film so that the camera's sensors will operate
correctly. This adjustment is also located on the main circuit. You'll
want to check several light levels and set the camera for optimal
performance throughout the range -- a little high at bright light, a
little low at low light, dead on at mid-range, for example.
Last, and functionally least, check and adjust the meter itself. Since
the meter needle is an indicator only, it doesn't actually "control" any
function. You'll want to check it for accuracy with a known-standard
lens, on a calibrated light source, at several light levels. And don't
forget that light entering the eyepiece will affect the needle's
reading, too. If the meter's error is linear, the adjustment is by
turning an eccentric on the ASA cam's follower. If the error isn't
linear, you've got trouble -- that won't happen unless something's
really wrong!
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